The present invention relates to an optical fiber terminating device and a method of terminating optical fibers in which the ends of a plurality of fibers are permanently secured in a receptacle.
The advantages of optical fibers, over copper conductors, for signal transmission are well known and include, for example, broad bandwidth and immunity to inductive pick up. However a particular problem with optical fibers is that of termination to facilitate splicing and switching etc. Unfortunately developments which have improved transmission qualities have resulted in fibers having a small outer diameter with an even smaller transmission core. Terminating monomode fibers having a small outer diameter (in the range of two hundred micron down to ten micron) is therefore particularly difficult.
Optical fibers are preferably terminated in groups or bundles rather than individually. This not only facilitates mechanical handling of the fibers but also allows additional functions to be provided, for example signal switching and multiplexing. A method of terminating small diameter fibers is shown in British Pat. No.
1524874 of Chinnock. FIG. 1 of this patent shows a receptacle in the form of a holder 10 in two Sections 11 and 12. Each section has a series of parallel grooves having an internal angle of ninety degrees. A fiber is placed in each of the grooves of Section 11 and then covered by a co-operating groove in Section 12. The fibers are then permanently secured by an expoxy adhesive.
In the above known terminating device the relative position of the fibers can be maintained within a very accurate tolerance range. However a disadvantage of the device is that it only provides a linear band of fibers and not a multi layer array, the latter being desirable in many applications. A multi layer array could be fabricated by securing a plurality of holders together or alternatively, intermediate holder sections may be provided with grooves on both sides. However both of these techniques result in an array in which the distance between fibers is relatively very large.
Closely packed arrays may be produced for large diameter multimode fibers by known techniques. An example of grouping large diameter fibers is shown by Tomlinson in U.S. Pat. No, 4,208,094. However it must be realised that handling large diameter fibers is relatively easy and represents a totally different branch of the optical fiber art. It is therefore possible to glue seven large diameter fibers together to produce an array consisting solely of fibers and glue. This approach would not be suitable for small diameter fibers which are very delicate. Before being glued, the seven fibers of Tomlinson are supported in a "V" shaped groove with three dummy fibers. The groove is formed in a support block and techniques are known for providing a groove which is accurate enough for large diameter fibers. However such a groove could not be machined to the required tolerances for small diameter fibers.